Question

Robert is hosting a backyard barbecue. He uses a charcoal fire to grill the chicken. The chicken cooks, but it never touches the fire directly. What energy transformation occurs as the chicken cooks?

Answer 1

Answer:

From chemical energy, to thermal energy. Which can be transfered via radiation or convection.

Explanation:

In our world, energy is constantly changing from one form, to another. The most basic law of physics is that energy cannot be created, nor destroyed, it can only change form.

This law allows us to do many calculations accurately.

In cooking, you have a source of energy, that heats up food, and then the food is cooked. In the question, there are a few energy convertions that take place.

The chemical energy stored in the coal is being released in the form of thermal energy.

When thermal energy is released, it can be transfered into the environment in three ways. Conduction, convection, and radiation.

Conduction is the transfer of thermal energy through two objects that are in direct contact with each other. However, since the question stated that the chicken doesn't directly touch the fire, conduction cannot occur.

Convection is the transfer of thermal energy, through a medium (usually air. In this example, the chicken is on a barbeque, so what happens is the charcoal transfers the thermal energy to the air around it, and when air heats up, it rises and transfers its energy to the environment as it rises (in this case, it would transfer a lot of that heat to the chicken).

Radiation is the transfer of thermal energy, without the need for a medium. We usually think of radiation as coming from the sun, and this is true because infrared waves are a form of radiation that can travel through space. Since the coal is producing radiation, it will travel until it comes into contact with something, this could be the chicken directly above it, or the people around the fire.

Answer 2

As the chicken cooks (and if it doesn't directly touch the fire), energy goes through the chemical, radiant, then thermal stages respectively.

The charcoal fire releases chemical energy. The heat of the fire is radiant, and the thermal (heat) of the fire cooks the chicken.